Apparatus for extruding prestressed concrete products



Aug 21, 1962 R. HANNAN, JR., ETAL 3,649,787

APPARATUS FOR EXTRUDING PRESTRESSED CONCRETE PRODUCTS Filed April 6,1959 N l. l Il Hannan NVENTORS BY WW HenrH Ralph Hannan cfr.

Il Illll llllll United States Patent O 3,049,787 APPARATUS FOR EXTRUDINGPRESTRESSED CONCRETE PRODUCTS Ralph Hannan, Jr., 4741 NE. Davis St., andHenry Hannan, 3525 NE. Going St., both of Portland, Oreg. Filed Apr. 6,1959, Ser. No. 804,206 1 Claim. (Cl. 25-118) lrI`his invention relatesto an apparatus for making prestressed concrete products. It pertainsparticularly to an apparatus for making beams, poles, piling, streetlight stands, and similar pnoducts from prestressed concrete.

It is the general o'bject of this invention to provide an apparatus `forextruding elongated prestressed concrete products of uniform compositionand high strength. These products may be either solid or hollow and maybe formed in lengths of several hundred feet which then may be dividedinto shorter lengths suitable for the contemplated end use.

In the drawings:

FIG. 1 is a side elevation of the presently described apparatus;

FIG. 2 is a transverse sectional view taken along line 2 2 of FIG. 1;

FIG. 3 is a longitudinal sectional view of the apparatus; and

I`FIG. 4 is a perspective View 'of an extruded, prestressed concretepole produced by the apparatus of FIGS. 1-3.

In general, the herein described method `of forming prestressed concreteobjects comprises rst tensioning at least one cable arrangedsubstantially horizontally above a casting bed. The cable and castingbed extend outwardly from a vertically arranged abutment. An uncured,selfsustaining concrete mix is extruded from a receptacle upon the bedand against the abutment. During this operation the receptacle ispropelled along the bed principally by the propelling force created bythe extrusion of the concrete against the abutment. The extrudedconcrete is molded about the cable to the desired exteriorconfiguration, after which the concrete is permitted to set. The tensionthen is released on the cable, after which the extrusion may be cut intolengths.

The apparatus of the invention broadly comprises means for elfectuatingthe foregoing method steps.

Considering the foregoing in greater detail and with reference to thedrawings:

In practicing the invention there is provided first a casting oor whichmay zbe made of concrete and covered with a release composition to whichmolded prestressed concrete objects will not stick. Fixed to the castingoor are a pair tof anchor blocks 12, 14 which may be spaced apart by asmuch as several hundred feet. One of the anchor blocks, e.g. block 14,is provided with a vertical abutment face 16.

Cables 18 are mounted between blocks 12, 14 at spacings determined bythe requirements of the prestressed product. Although various means ofsecuring the cables may be employed, a convenient means comprisespassing them through block 14 and securing their ends with clamps 20.The even surface of abutment 16 thus is preserved.

The other ends of cables 18 may be secured to bolts 22 which penetrateblock 12 and are secured by nuts 24. Thus the cables may be tensioned tothe `desired degree by means of jacks or `other suitable tensioningapparatus, after which the tension is maintained by adjustment of nuts24.

The extruding apparatus is mounted on a vehicle which is guided byca'bles 18 and which traverses the casting bed between the anchorblocks. In the illustrated form of the invention the vehicle comprises aframe 26 one end of which is supported on wheels 28 moving `on tracks3G.

3,049,787 Patented Aug. 2l, 1962 lCC Frame 26 supports a motor 32coupled through a gear box 34 Ito a drive sprocket 36. This spnocketdrives a chain 38 which is connected to and drives a second sprocket 40keyed to the shaft of a screw 42. The screw is housed in a screw case 44with `which communicates the lower end of a hopper 45.

An outwardly flaring mold 46 is bolted Vto the trailing end of screwfcase 44. The mold is of dimensions determined by the size of the objectto be extruded. It is three sided, the surface yof casting bed 10forming the bottom.

Guideways 50 extend longitudinally through the mold. These receivecables 18 which penetrate to the interior of the mold in -the mannerindicated particularly in FIG. 3.

lIn the event that hollow articles are to be extruded, a coring element52 may be afxed to the end of screw 42 as a longitudinal extensionthereof. In the illustrated form of the invention, the coring member isconical so that the contour of its outer surface parallels the contour0f the inner surface of mold 46. A passageway of the desired `width thusis provided between these two members.

Operation In extruding iinished prestressed concrete articles 54 by thepresent invention, cables 1-8 are threaded through guideways 50 in mold46 and connected at one end to auchor block 14 by clamps 20 and at theother end to anchor block 12 by eye bolts 22.

The required tension is placed on the cables by means of jacks andmaintained `by adjusting nuts 24.

The apparatus then is placed with the open trailing end of mold 46squarely against abutment surface 16 of anchor block 14. A stiffconcrete mix, e.g. lone having a moisture content of `fro-m 515%, byWeight, is introduced into hopper 45.

:Worm 42 is driven by motor 32 whereupon the concrete mix is extrudedthrough the passageway between coring element 52 and mold 46. Theresulting pressure against abutment surface 16 drives the vehiclemounting hopper 45 across casting bed 1l) in a direction determined bycables 18 and guides y50, and at a rate determined by the rate ofextrusion of the concrete product.

|Because of its inherent stiffness, the concrete retains the shapeimparted to it by mold 46 and coring member 52. In addition, itsinterior surface is trowled smooth 'by the rotary motion of the coriugelement.

The operation is carried on continuously until a product of the desiredlength has been extruded about the ten sioned cables. This product maybe several 'hundred feet long. It is permitted to cure, after whichcables 18 may be released and the product cut into lengths suitable foruse `as prestressed concrete pipe, poles, plings and the like.

Accordingly it is apparent that by the present invention we haveprovided an apparatus for producing prestressed concrete articles ofVarious types, al1 of which are characterized by great strength, and auniform surface. The technique permits the production of either solid orhollow articles Without using forms, and the linished articles can beproduced continuously at loW oost and then stockpiled. Hence there isafforded an economical, efficient procedure for the large scaleproduction of such articles.

It is to be understood that the form of our invention herein shown and`described is to be taken as a preferred example of the same and thatvarious changes in the shape, size and arrangement lof parts may beresorted to without departing from the spirit of our invention or thescope of the subjoined claim.

Having thus described our invention, we claim:

Apparatus for forming prestressed elongated concrete articles comprisingin combination a horizontal elongated a, 049, ver

casting bed, elongated track means substantially parallel to the bed, avehicle, wheel means on the leading end of the vehicle engaging thetrack means for movably supporting and guiding the leading portion ofthe vehicle on the track means, extrusion means, a hollow mold on thetrailing end yof the vehicle communicating with the extrusion means forreceiving and forming extruded concrete in a continuous elongated shapeupon longitudinal movement of the vehicle, the mold having elongatedcafble guide means extending therethrough into the hollow thereof andlongitudinally of the vehicle, a cable snugly but slidahly conned in theguide means yand eX- tending through the hollow of the mold, stationaryanchor means spaced apart at opposite ends of the casting bed, andvtensioning means on the anchor means releasably securing the cable atits opposite ends in tensioned condition `between the stationary anchormeans, said cable serving as a guide for the trailing end of the vehicleinA [i the longitudinal extruding movement of the latter and formingreinforcing means for the extruded concrete articles said guide meansbeing so located that said cafble is clear of the extruding unit.

References Cited in the le of this patent UNITED STATES PATENTS

